1. Field
The subject invention is in the field of equipment and apparatus for reducing the perceivable noise produced by the effluent from gas turbine engines, i.e. jet engines. More particularly, it is in the field of lobed mixers used for suppressing the noise caused by jet engine effluent. Limits on the perceived noise produced by jet engines on airplanes are continuously becoming more restrictive and more prevalent with sophisticated noise measuring systems installed at many airports to enforce the restrictions.
2. Prior Art
The U.S. Patents listed below provide a sample of the prior art in this particular field:
3,153,310 4,835,961 4,077,206 4,909,346 4,148,878 5,216,879 4,819,425 5,638,675
There is also applicable prior art in a NASA report: NASA CR114584 titled "Task V Noise Suppression Of Improved Augmentors For Jet Stol Aircraft." This report describes a flat array of rectangular corrugations with a relatively hotter and higher velocity gas mixture flowing on one side of the corrugations and relatively cooler, lower velocity air flowing on the other side, as different from having the two flows separated by a flat plate. Tests indicated that the corrugations augmented mixing of the two flows and it is well known in the art that such mixing reduces perceivable noise produced by the effluent. It is also known in the art that the amount of suppression increases with increases in the ratio of wetted areas of the passageways involved to the cross sectional areas of the passageways and with decreasing width dimensions of the convolutions of the passageways.
In view of these facts and the need for improved suppression of the perceivable noise produced by jet engines, the primary objective of the subject invention is to provide a jet engine noise suppressing mixer having passageways having relatively high ratios of wetted areas to cross sectional areas in its passageways and having corrugations in the passageways having relatively small width dimensions relative to the radius of the mixer.